chore(ci): add test matrix for v21

Author: metcoder95

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [16.x, 18.x, 20.x]
+        node: [16.x, 18.x, 20.x, 21.x]
     name: Node ${{ matrix.node }}
     steps:
       - uses: actions/checkout@v4